1. Field of Art
The present invention relates generally to the preparation of molds used in a so-called lost wax casting process, and particularly to a process and apparatus for dewaxing ceramic shell molds by use of a superheated high temperature steam to melt and remove the wax from the molds prepared by coating a slurry and stucco particles over the wax masters.
2. Prior Art
In the lost wax casting process, it is a common practice to use an autoclave for melting the wax contained in the green ceramic shell molds formed by coating a slurry and stucco particles to allow the molten wax to leave the molds. In the conventional dewaxing step, a shell mold tree is put into a dewaxing tank of the autoclave with the sprue port thereof facing downwardly, followed by a rapid heating by means of superheated steam. However, in the preceding steps, the shell mold tree is held in the condition that the sprue rod protruding through the sprue port extends upwardly. In detail, in the coating step, the wax master tree is suspended from the sprue rod and subjected to repeated dippings into the slurry and stucco reservoirs followed by drying. Then, prior to introducing the dried shell mold tree into the dewaxing tank, the tree must be inverted to allow the molten wax to flow out of the mold cavities.
After the completion of the dewaxing operation, the dewaxed shell mold tree should be again inverted to be held in the initial condition at which the sprue rod protruding through the sprue port extends upwardly, in order to effect a complete combustion of the remaining wax at the subsequent step of sintering the stucco particles to form the finished ceramic shell molds.
By the use of the conventional autoclave for dewaxing, the green wax master trees must be inverted upside down by hand before they are introduced into the autoclave, and they must be again inverted to the initial or normal condition after they are dewaxed to be ready for subjecting them to the subsequent sintering step. These repeated inversion operations have hitherto been carried out manually to lower the operation efficiency. Manual operations also result in an increase of production cost.